Acrylic elastomers and crosslinked products thereof are superior in physical properties including heat oxidizing resistance, oil resistance, mechanical properties, and compression set properties and have been used widely as the materials for hose parts, seal parts, and antivibration rubber parts in automobile engine room. Under increasing demand for extensive exhaust gas purification and higher engine output, there is recently a need for materials higher in heat oxidizing resistance and acid resistance for these automobile parts.
For example, a fluorine-based elastomer, which is higher in durability and acid resistance than acrylic elastomers, may be used to increase reliability of rubber parts by improving these properties. However, such a fluorine-based elastomer is lower in low-temperature resistance and also expensive and thus, not suited as a material for auto parts that demand low cost and high reliability simultaneously.
Accordingly, a method of using a fluorine-based elastomer and another elastomer in combination was proposed. For example, it is possible to improve practical durability by laminating a fluorine-based elastomer on the region that has particularly a problem of durability.
On the other hand if a laminate is formed with a fluorine-based elastomer, an important property demanded for the laminate is interlayer adhesiveness thereof. When the interlayer adhesion strength is low, the laminate is less reliable. In particular, as fluorine-based elastomers are less adhesive to other materials, it is extremely important, for preparation of a less-expensive laminate superior in durability from a fluorine-based elastomer and an acrylic elastomer, to increase the adhesion strength of these elastomer layers.
Methods of increasing the adhesiveness of a fluorine-based elastomer include a method of treating the surface of a fluorine-based elastomer layer with metal sodium solution (see, for example, Patent Document 1), a method by discharge treatment (see, for example, Patent Document 2), a method by plasma treatment (see, for example, Patent Document 3), and others. Also proposed was a laminate with physical properties (such as low-temperature embrittlement resistance) and adhesiveness to non-fluorine rubber layers improved by mixing a fluoroplastic resin in a particular structure with a fluorine rubber (see, for example, Patent Document 4).